Poly(ADP-ribosyl)ation of polynucleosomes causes relaxation of chromatin structure.
When rat pancreatic polynucleosomes were poly(ADP-ribosyl)ated with purified calf thymus poly(ADP-ribose) polymerase and examined by electron microscopy, a relaxation of their native zigzag structure was observed. At high ionic strengths control nucleosomes condensed into 250-A-thick fibers, but poly(ADP-ribosyl)ated polynucleosomes did not; they showed a close resemblance to chromatin depleted of histone H1. The relaxed state of poly(ADP-ribosyl)ated polynucleosomes was also confirmed by sedimentation velocity analysis. Histone H1 was found to be the major histone acceptor of poly(ADP-ribose). Poly(ADP-ribose) linked to histone H1 did not seem to cause its dissociation from the chromatin, but it impaired significantly its effect on chromatin condensation.
D000818:Animals; D002843:Chromatin / Q000648:ultrastructure*; D006657:Histones / Q000378:metabolism*; D008854:Microscopy, Electron; D009702:Nucleoside Diphosphate Sugars / Q000378:metabolism*; D009707:Nucleosomes / Q000378:metabolism*; D011064:Poly Adenosine Diphosphate Ribose / Q000378:metabolism*; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D051381:Rats; D014461:Ultracentrifugation
D002843:Chromatin; D006657:Histones; D009702:Nucleoside Diphosphate Sugars; D009707:Nucleosomes; D011064:Poly Adenosine Diphosphate Ribose; D011065:Poly(ADP-ribose) Polymerases